Photos: Houston tries to keep cool amid heat wave

Update (Wednesday, 5:15 a.m.): Wednesday’s forecast in Houston calls for a high of 94 degrees and a 20 percent chance of rain.

The Texas Commission on Environmental Quality is reporting that ozone levels in Houston are unhealthy for sensitive groups.

The ozone watch is also in force for Galveston and Brazoria counties.

Atmospheric conditions are expected to be favorable for producing high levels of ozone pollution until sunset. Ozone warnings will be issued if air pollution levels are detected at unhealthy levels.

Elevated concentrations of ozone can act as a lung irritant. People with chronic lung disease such as asthma and emphysema, the elderly and small children are particularly sensitive to ozone and should attempt to avoid exposure by staying indoors.

The National Weather Service issued a heat advisory for Houston today. High temperatures could return later today. NWS forecasters urged residents who are spending time outside today to limit strenuous activities, wear lightweight and loose-fitting clothing and drink plenty of water.